CN101183783A - Graded hyperbolic anti-TA transient saturation differential protection method - Google Patents

Abstract

The invention relates to a differential protecting method for gradual changing hyperbolic high resistant TA transient saturation, which is characterized in that the braking curve is hyperbola; gradual changing technique is adopted and the braking current is calculated through a new algorithm; the differential protection misoperation is prevented under the circumstances of the restraining quantity collapsing in the clearance of external faults or the differential TA saturation during the faults; the operation equation is as above; wherein Id is the differential current; Iz is the braking current; K(Iz) is the gradual slope; Kc is the slope of the asymptotic line for the gradual braking property of the hyperbola; Iq is the starting current. With the gradual changing technique, the invention has the advantages of remarkable effects on the clearance of external faults, the collapsing of the restraining quantity and the differential faults caused by the TA transient saturation which is caused by the aperiodic component during the failure, resolving the technical difficulty of TA transient saturation potential misoperation in the prior differential protection.

Description

The graded hyperbolic anti-TA transient saturation differential guard method

Technical field

The present invention relates to the field of power Principles of Relay Protection, specifically relate to a kind of graded hyperbolic anti-TA transient saturation differential protection philosophy.Belong to the power automation technical field.

Background technology

During the outer fault of generator or transformer circuit district inner region, short circuit current is very big, and damping time constant is big, contain in the short circuit current aperiodic transient state component and decay slowly, will cause seriously that the TA iron core is saturated, cause TA progress of disease characteristic variation.Add differential protection both sides TA difference, no-load voltage ratio difference, the load that model is different, each TA loop degree of saturation is inconsistent.The spill current of differential protection strengthens during external area error, may brake incessantly by the normal rate braking characteristic, produces malfunction; And during troubles inside the sample space because the waveform generation distortion, differential protection also might be by the mistake locking.

TA serious saturated after, general residual have remanent magnetism, easier to be saturated, even both sides TA characteristic is identical, because very big difference stream still may appear in the remanent magnetism difference.The appearance of big unit increases the power frequency short-circuit current multiple, has deepened the saturated of TA, is a serious test to the current measurement circuit of protecting, and longitudinal difference protection external short-circuit unsymmetrical current is increased severely, and causes the malfunction of differential protection easily.This just need take into full account these factors at aspects such as TA type selecting, filtering algorithm, protective features; further strengthen protection power pack The Characteristic Study; on the protection philosophy research a kind of novel differential, can suppress the saturated differential misoperation that may cause of TA transient state.

Differential protection present many employings ratio braking principle and scalar product braking principle, saturated for CT transient state technically, particularly the less situation adaptibility to response of external area error excision, stalling current a little less than, cause unnecessary malfunction through regular meeting.

Summary of the invention

For solving the deficiencies in the prior art; the present invention is based on research to TA transient state saturation characteristic; and, develop the saturated graded hyperbolic anti-TA transient saturation differential protection philosophy of high anti-TA transient in conjunction with advanced principles such as waveform recognition technology, waveform Predicting Technique and dynamic data windows.

For achieving the above object, the present invention is achieved by the following technical solutions:

A kind of graded hyperbolic anti-TA transient saturation differential protection philosophy, it is characterized in that braking curve is no longer constant as conventional ratio braking slope, but introduce hyperbolic system moving curve feature, adopt the technology of gradual change, and ask for stalling current with new algorithm, the braking amount descends suddenly when external area error excises, and perhaps under the situation that differential TA is saturated when fault, prevents differential protection misoperation; Its operation equation is:

$\left\{\begin{array}{c}{I}_d=K\left(I_z\right)I_z\\ K\left(I_z\right)=\sqrt{{K_c}^2+{(I_q/I_z)}^2}\end{array}\right.$

As can be known: $I_d=\sqrt{{\left(K_c{I}_z\right)}^2+{\left(I_q\right)}^2}$

$\frac{{I_d}^2}{{I_q}^2}-\frac{{I_z}^2}{{(I_q/K_c)}^2}=1$

When being two side transformer differentials:

$I_d=|{\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2|$

${\stackrel{\·}{I}}_1^{\′}=\max \left\{\right|{\stackrel{\·}{I}}_1|,|{\stackrel{\·}{I}}_2\left|\right\},$ Get certain with the maximum in each side electric current of famous prime minister;

${\stackrel{\·}{I}}_2^{\′}=({\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2)-\max ({\stackrel{\·}{I}}_1,{\stackrel{\·}{I}}_2)$

$\mathrm{\φ}=\∠({\stackrel{\·}{I}}_1^{\′},{\stackrel{\·}{I}}_2^{\′})$

In the formula: I _dBe differential current; I _zBe stalling current; K (I _z) for the slope of gradual change; K _cAsymptote slope for hyperbola gradual change braking characteristic; I _qBe starting current;

---be respectively transformer each side electric current with the famous prime minister;

For transformer with the maximum in each side electric current of famous prime minister;

For certain with each side current phasor of famous prime minister and with each side electric current in the maximum vector poor; φ is

With

Between angle.

Aforesaid graded hyperbolic anti-TA transient saturation differential protection philosophy is characterized in that above-mentioned differential current I _dWith stalling current I _zConstituted hyperbola.

Aforesaid graded hyperbolic anti-TA transient saturation differential protection philosophy is characterized in that above-mentioned K (I _z) for becoming restraint coefficient, its minimum value is K _c, more safer than traditional restraint coefficient.

Aforesaid graded hyperbolic anti-TA transient saturation differential protection philosophy is characterized in that the asymptote slope K of above-mentioned hyperbola gradual change braking characteristic _cAdjust and be the slope K of traditional ratio-restrained characteristic _Z

The invention has the beneficial effects as follows: braking curve of the present invention is no longer constant as conventional ratio braking slope; introduce hyperbolic system moving curve feature; adopt the technology of gradual change; and ask for stalling current with new algorithm; has the effect of highly significant for the saturated differential misoperation that may cause of TA transient state that external area error excision, braking amount descend suddenly, aperiodic component causes in the failure process; can prevent differential protection misoperation, thereby solve the technological difficulties of the saturated potential malfunction of TA transient state in the present differential protection.

Description of drawings

Fig. 1 transformer differential protection exchanges and inserts the loop schematic diagram;

Fig. 2 becomes braking characteristic curve and common braking curve comparison diagram (dotted portion is common braking curve) for the gradual change hyperbola;

Fig. 3 disjunction gate brake type transformer differential protection logic diagram;

Fig. 4 " phase-splitting " brake type transformer differential protection logic diagram.

Specific embodiments

Below in conjunction with accompanying drawing the present invention is done concrete being described below.

The present invention introduces hyperbolic system moving curve feature, adopts the technology of gradual change, has formed the saturated differential protection philosophy of the high anti-CT transient state of gradual change hyperbola.

(1) operation equation

Hyperbola becomes the braking characteristic differential principle:

Operation equation: $\left\{\begin{array}{c}{I}_d=K\left(I_z\right)I_z\\ K\left(I_z\right)=\sqrt{{K_c}^2+{(I_q/I_z)}^2}\end{array}\right.---\left(1\right)$

That is:

$I_d=\sqrt{{\left(K_c{I}_z\right)}^2+{\left(I_q\right)}^2}---\left(2\right)$

$\frac{{I_d}^2}{{I_q}^2}-\frac{{I_z}^2}{{(I_q/K_c)}^2}=1---\left(3\right)$

In the formula: I _dBe differential current; I _zBe stalling current; K (I _z) for the slope of gradual change; K _cBecome the asymptote slope of braking characteristic for hyperbola; I _qBe starting current.

By formula (1) as can be known, K (I _z) be the slope of gradual change, by formula (2) as can be known, differential current I _dWith stalling current I _zConstituted hyperbola.The asymptote slope K of hyperbola gradual change braking characteristic _cSuggestion is adjusted and is the slope K of traditional ratio-restrained characteristic _Z

(2) braking characteristic

Fig. 1 inserts the loop schematic diagram for transformer differential protection exchanges, be example with three side transformer differentials protection among Fig. 1, and the braking characteristic of hyperbola gradual change braking characteristic curve is described.

In the formula (1):

$I_d=|{\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2+{\stackrel{\·}{I}}_3|---\left(4\right)$

${\stackrel{\·}{I}}_1^{\′}=\max \left\{\right|{\stackrel{\·}{I}}_1|,|{\stackrel{\·}{I}}_2\left|\right|{\stackrel{\·}{I}}_3\left|\right\},$ Get certain with the maximum in each side electric current of famous prime minister;

${\stackrel{\·}{I}}_2^{\′}=({\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2+{\stackrel{\·}{I}}_3)-\max ({\stackrel{\·}{I}}_1,{\stackrel{\·}{I}}_2{\stackrel{\·}{I}}_3)$

$\mathrm{\φ}=\∠({\stackrel{\·}{I}}_1^{\′},{\stackrel{\·}{I}}_2^{\′})$

In the formula: I _dBe differential current; I _zBe stalling current; K (I _z) for the slope of gradual change; K _cAsymptote slope for hyperbola gradual change braking characteristic; I _qBe starting current;

Be respectively transformer each side electric current with the famous prime minister;

For transformer with the maximum in each side electric current of famous prime minister;

For certain with each side current phasor of famous prime minister and with each side electric current in the maximum vector poor; φ is

With

Between angle.

Braking characteristic as shown in Figure 2, Fig. 2 is that the gradual change hyperbola becomes braking characteristic curve and common braking curve comparison diagram, dotted portion is common braking curve.Hyperbola gradual change braking characteristic curve has braking at the very start, adopts starting current identical with traditional ratio-restrained characteristic and braking slope, the restraint coefficient K (I of hyperbola gradual change _Res) minimum value be K _c, than traditional ratio-restrained characteristic safety.

For troubles inside the sample space, owing to introduce the phase characteristic of differential each side electric current, stalling current is about 0, and is perhaps very little, for minor failure in the district suitable sensitivity arranged still.

For external area error, by formula (5) as can be known, stalling current no longer is 0, and is

And because the phase characteristic of each side electric current, differential current is 0, and is perhaps very little, can guarantee that differential protection reliably is failure to actuate.

Transient state saturation problem for the external area error excision, it is saturated that the transient state fault current of passing through property may cause transformer both sides TA to enter transient state, after the external area error excision, electric current reverts to load current, but because the transient characterisitics difference of TA, bigger difference stream (the amplitude conversion of both sides TA is normal, and 10 °～30 ° angular difference appears in phase place) may appear in secondary current, this moment, operating point often dropped near the flex point of brakeless characteristic, the malfunction of differential possibility.And hyperbola gradual change braking characteristic can be lifted to starting threshold adaptively $\left(\sqrt{1+\frac{{I_z}^2}{{(I_q/K_c)}^2}}\right)I_q,$ Effectively prevent CT transient state saturation problem, also can prevent effectively that differential protection from withdrawing from malfunction possible in the saturation history at CT.Than the variation track by recognition differential streaming current and stalling current, when the operating point of ratio brake differential protection forwarded active region to by the braking district, differential protection adopted the strategy of little deferred action, can further optimize differential rapidity and sensitivity.

(3) logic diagram

The logic diagram of transformer differential protection such as Fig. 3 or shown in Figure 4.Fig. 3 represents disjunction gate braking principle longitudinal difference protection block diagram; Fig. 4 is a phase-splitting braking principle longitudinal difference protection block diagram.

(4) parameter related to the present invention adjusts

(1) asymptote slope K _c

The asymptote slope K _cThe principle of adjusting, the maximum transient material unaccounted for stream that produces when escaping the outlet three-phase shortcircuit adjust (crossing the top of the oblique line of flex point) by outlet external area error maximum difference stream corresponding points.The value of scalar product restraint coefficient and ratio brake coefficient is basic identical.Generally

K _c＝0.4～0.5

(2) starting current I _q

The principle of adjusting: can reliably escape the maximum material unaccounted for stream of generator transformer when normally moving.Generally

I _q＝(0.4～0.5)I _e

Below announced the present invention with preferred embodiment, so it is not that all employings are equal to the technical scheme that mode obtained of replacement or equivalent transformation, all drop in protection scope of the present invention in order to restriction the present invention.

Claims (4)

1. graded hyperbolic anti-TA transient saturation differential guard method, it is characterized in that, braking curve is no longer constant as conventional ratio braking slope, but introduce hyperbolic system moving curve feature, adopt the technology of gradual change, and ask for stalling current with new algorithm, the braking amount descends suddenly when external area error excises, perhaps under the situation that differential TA is saturated when fault, prevent differential protection misoperation; Its operation equation is:

$\left\{\begin{array}{c}{I}_d=K\left(I_z\right)I_z\\ K\left(I_z\right)=\sqrt{{K_c}^2+{(I_q/I_z)}^2}\end{array}\right.$

As can be known: $I_d=\sqrt{{\left(K_c{I}_z\right)}^2+{\left(I_q\right)}^2}$

$\frac{{I_d}^2}{{I_q}^2}-\frac{{I_z}^2}{{(I_q/K_c)}^2}=1$

When being two side transformer differentials:

$I_d=|{\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2|$

${\stackrel{\·}{I}}_1^{\′}=\max \left\{\right|{\stackrel{\·}{I}}_1|,|{\stackrel{\·}{I}}_2\left|\right\},$ Get certain with the maximum in each side electric current of famous prime minister;

${\stackrel{\·}{I}}_2^{\′}=({\stackrel{\·}{I}}_1+{\stackrel{\·}{I}}_2)-\max ({\stackrel{\·}{I}}_1,{\stackrel{\·}{I}}_2)$

$\mathrm{\φ}=\∠({\stackrel{\·}{I}}_1^{\′},{\stackrel{\·}{I}}_2^{\′})$

In the formula: I _dBe differential current; I _zBe stalling current; K (I _z) for the slope of gradual change; K _cAsymptote slope for hyperbola gradual change braking characteristic; I _qBe starting current;

---be respectively transformer each side electric current with the famous prime minister;

For transformer with the maximum in each side electric current of famous prime minister; For certain with each side current phasor of famous prime minister and with each side electric current in the maximum vector poor; φ is

With Between angle.

2. graded hyperbolic anti-TA transient saturation differential guard method according to claim 1 is characterized in that, above-mentioned differential current I _dWith stalling current I _zConstituted hyperbola on the two-dimensional coordinate.

3. graded hyperbolic anti-TA transient saturation differential guard method according to claim 1 is characterized in that, above-mentioned K (I _z) for becoming restraint coefficient, its minimum value is K _c

4. graded hyperbolic anti-TA transient saturation differential guard method according to claim 1 is characterized in that, the asymptote slope K of above-mentioned hyperbola gradual change braking characteristic _cAdjust and be the slope K of traditional ratio-restrained characteristic _Z

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